Plasma treatment apparatus and method of manufacturing optical parts using the same

ABSTRACT

A plasma treatment apparatus for treating a surface of an object of treatment comprises a pressure reducible container, a gas supply means for supplying gas into the container for plasma excitation, an evacuation means for evacuating the inside of the container and a microwave supply means for supplying a microwave into the container. The surface of said microwave supply means located opposite to said object of treatment is a non-planar surface. A film coat showing an excellent intra-surface uniformity and practically free from pin holes and local defects can be formed by means of such an apparatus.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a plasma treatment apparatus adapted totreating the surface of an optical part having a non-planar surface tobe treated such as a convex lens, a concave lens or a concave mirror.More broadly, it relates to a technological field of manufacturingoptical parts, using such an apparatus.

[0003] 2. Related Background Art

[0004] There is a demand for improved surface treatment techniques to beused for cleaning and/or forming a film coat on objects of treatmenthaving a non-planar surface to be treated.

[0005] An anti-reflection film to be formed on a convex lens may be atypical example of film coat of the type under consideration.

[0006] Japanese Patent Application Laid-Open No. 2-232367 describes atypical known film forming method employing PVD, which may besputtering.

[0007] Since PVD is not highly effective for forming a film coat on anobject having an undulated or otherwise non-planar surface, theinventors of the present invention have been trying to form a film coaton objects of treatment by CVD.

[0008] Since the technique of thermal CVD has a disadvantage ofproducing thermal deformations, it is not adapted to forming a film coatof the type under consideration. On the other hand, the technique ofoptical CVD is not satisfactory in terms of throughput.

[0009] Meanwhile, even the technique of plasma excitation CVD (PECVD)using an RF power source with a frequency of 13.56 MHz is notsatisfactory for producing an anti-reflection film having a highertransmission coefficient (lower absorption coefficient) than thosecurrently obtainable by PVD and having improved light resistance andenvironment resistance. Therefore, a PECVD technique that can produce ahigher plasma density will have to be used.

[0010] A technique of electrodeless PECVD using a microwave such aselectron-cyclotron-resonance CVD (ECR-PECVD) is known to produce a highdensity plasma exceeding the density level of 10¹⁰ cm⁻³.

[0011]FIG. 24 of the accompanying drawings is a schematic crosssectional view of a plasma treatment apparatus disclosed in JapanesePatent Application Laid-Open No. 6-216047.

[0012] Referring to FIG. 24, this apparatus comprises a plasma generatorchamber 2 and a treatment chamber 4, of which the plasma generatorchamber 2 contains therein microwave power introducing means 5, 6, 8 anda magnetic field applying means 10 and is connected to a plasma sourcegas introduction system 20 while the treatment chamber 4 is connected toa chemically reactive material gas introduction system 22, sample table14 of the apparatus being connected to an RF power introducing means 18.Additionally, a control unit 27 is provided to modulate the power outputof the microwave power generator 8 and that of the RF power generator18. With this arrangement, the RF power and the microwave power aremodulated synchronously and the film forming conditions are alternatelymodified in favor of film forming and in favor of sputtering/etching toproduce a CVD film.

[0013] While an anti-reflection film formed on a convex lens by means ofan apparatus as shown in FIG. 24 is dense and fine in average, it isrelatively poor in terms of intra-surface uniformity. More specifically,reaction by-products can frequently remain on and near the treatedsurface to give rise to areas showing different compositional ratios.Such by-products can adhere to the surface, and, if they are removedduring or after the film-forming process, pin holes can be produced inthe film.

SUMMARY OF THE INVENTION

[0014] It is therefore an object of the present invention to provide aplasma treatment apparatus that can produce a film coat substantiallyfree from pin holes and other local defects and showing an excellentintra-surface uniformity and an outstanding coating effect.

[0015] According to an aspect of the invention, there is provided aplasma treatment apparatus for treating a surface of an object oftreatment, comprising a pressure reducible container, a gas supply meansfor supplying gas into the container for plasma excitation, anevacuation means for evacuating the inside of the container, and amicrowave supply means for supplying a microwave into the container, themicrowave supply means having a plurality of microwave emitting membersand its surface located opposite to the object of treatment beingdirected in a predetermined direction relative to the surface to betreated of the object of treatment.

[0016] According to another aspect of the invention, there is provided aplasma treatment apparatus for treating a surface of an object oftreatment, comprising a pressure reducible container, a gas supply meansfor supplying gas into the container for plasma excitation, anevacuation means for evacuating the inside of the container, and amicrowave supply means for supplying a microwave into the container, thesurface of the microwave supply means located opposite to the object oftreatment being a non-planar surface having a contour corresponding tothat of the surface to be treated of the object of treatment.

[0017] Preferably, the gas blow-in port of the gas supply means isarranged at an end of an antenna made of a conductor member and having aslot.

[0018] According to still another aspect of the invention, there isprovided a plasma treatment apparatus for treating a surface of anobject of treatment, comprising a container, a gas supply means forsupplying gas into the container for plasma excitation, an evacuationmeans for evacuating the inside of the container, and a microwave supplymeans for supplying a microwave into the container, the surface of themicrowave supply means located opposite to the object of treatment beinga non-planar surface having a contour corresponding to that of thesurface to be treated of the object of treatment and the non-planarsurface being formed of a microwave-transmitting dielectric.

[0019] Preferably, gas is supplied through a plurality of openingsarranged on the non-planar surface.

[0020] Preferably, the microwave supply means has an antenna made of aflat plate of a conductor and having a number of slots.

[0021] Still preferably the non-planar surface is a convex or concavespherical surface formed on the microwave-transmitting dielectric.

[0022] According to a still another aspect of the invention, there isprovided a method of manufacturing an optical part comprising a step oftreating a concave or convex surface of the optical part by means of aplasma treatment apparatus as defined above.

[0023] According to a further aspect of the invention, there is provideda plasma treatment apparatus for treating a surface of an object oftreatment by means of plasma, comprising a container, a gas supply meansfor supplying gas into the container for plasma excitation, and anevacuation means for evacuating the inside of the container, a part ofthe walls of the container being made of a dielectric plate of amaterial adapted to transmit microwaves, the dielectric plate having aconvex or concave spherical surface with a predetermined radius ofcurvature (ra), an antenna for emitting a microwave and an electrodeadapted to hold the object of treatment being arranged respectively atthe outside and at the inside of the container to sandwich thedielectric plate.

[0024] Preferably, the dielectric plate has a shower-head-like profileprovided with a plurality of gas supply holes for evenly supplying gasto the surface of the object of treatment.

[0025] Preferably, in a plasma treatment apparatus as defined above, theradius of curvature (ra) and the radius of aperture (da) of thedielectric plate are variable.

[0026] Still preferably, the distance (Tg) between the inner surface ofthe dielectric plate and the surface to be treated of the object oftreatment is between 10 mm and 50 mm.

[0027] Still preferably, the relative density difference of the plasmain the surface to be treated is suppressed to less than about 20%.

[0028] Still preferably, the variations in the plasma density due to thevariations in the thickness of the dielectric plate can be corrected bymaking at least the size, the profile or the number of the slots formedin the antenna to show a distribution pattern.

[0029] Preferably, the object of treatment is held by a support memberprovided with a rotary mechanism.

[0030] Preferably, the non-planar surface is a stepped surface obtainedby forming coaxial steps.

[0031] Preferably, the gas supply means has a stepped shower-head-likeprofile.

[0032] Preferably, the main body of the antenna has a spherical orstepped profile.

[0033] Then, the antenna having a spherical or stepped profile isarranged within the container.

[0034] Preferably, a non-planar surface is formed by using a pluralityof such antennas.

[0035] According to a still another aspect of the invention, there isalso provided a surface treatment method for treating the surface of anobject of treatment by means of an apparatus as defined above.

[0036] Preferably, the surface treatment consists in forming a thinfilm.

[0037] According to still another aspect of the invention, there isprovided a method of manufacturing an optical part by using a surfacetreatment method as defined above and forming an anti-reflection orreflection-boosting thin film on an object of treatment made of siliconoxide or calcium fluoride.

[0038] According to the invention, a dense and fine film can be obtainedbecause high density plasma excited by one or more than one microwavescan be confined within a narrow electric discharge space.

[0039] Additionally, according to the invention, a large surface can betreated uniformly by plasma because the surface to be treated is locatedin a region showing a uniform plasma density.

[0040] Still additionally, according to the invention, pin holes willhardly be produced on the treated surface because the volume of theelectric discharge space is reduced, the inside of the electricdischarge chamber can be evacuated easily by means of a vacuum pump witha relatively small evacuation capacity and the reaction by-products, ifany, can be quickly removed out of the electric discharge chamber. Auniform gas supply can be realized in a narrow space if a large numberof gas supply holes are formed in a dielectric so that a film showing aconstant compositional ratio may be formed on the surface.

BRIEF DESCRIPTION OF THE DRAWINGS

[0041]FIG. 1 is a schematic cross sectional view of an embodiment ofplasma treatment apparatus according to the invention.

[0042]FIG. 2 is a schematic perspective view of the non-planardielectric plate of the embodiment of FIG.

[0043]FIG. 3 is a schematic plan view of the conductor flat plateantenna of the embodiment of FIG. 1.

[0044]FIG. 4 is a graph showing the relationship between the gapseparating the dielectric plate and the object of treatment and theplasma density in the embodiment of FIG. 1.

[0045]FIG. 5 is a schematic side view of the non-planar profile of thedielectric plate used in the embodiment of FIG. 1 when treating thesurface of a convex lens whose largest thickness is less than 40 mm.

[0046]FIG. 6 is a schematic side view of the non-planar profile of thedielectric plate used in the embodiment of FIG. 1 when treating thesurface of a convex lens whose largest thickness is more than 40 mm.

[0047]FIG. 7 is a schematic cross sectional view of an embodimentobtained by modifying the embodiment of FIG. 1 so as to make themicrowave emitting surface of the dielectric plate show a steppedprofile.

[0048]FIGS. 8A and 8B are a schematic cross sectional view and aschematic plan view of the dielectric plate shown in FIG. 7.

[0049]FIG. 9 is a schematic cross sectional view of another embodimentof plasma treatment apparatus obtained by modifying the embodiment ofFIG. 1 and suitably adapted to surface treatment of a concave lens.

[0050]FIG. 10 is a graph showing the radial distance of the conductorflat plate antenna and the plasma density in different embodiments ofthe invention.

[0051]FIG. 11 is a schematic cross sectional view of still anotherembodiment of plasma treatment apparatus using a dielectric plate with amicrowave emitting surface having a stepped and substantially convexprofile.

[0052]FIGS. 12A and 12B are a schematic cross sectional view and aschematic plan view of the dielectric plate of the apparatus of FIG. 11.

[0053]FIG. 13 is a schematic cross sectional view of still anotherembodiment of plasma treatment apparatus obtained by modifying theembodiment of FIG. 1 and suitably adapted to surface treatment of aconvexo-convex lens.

[0054]FIG. 14 is a schematic cross sectional view of still anotherembodiment of plasma treatment apparatus obtained by modifying theembodiment of FIG. 9 and suitably adapted to surface treatment of aconcavo-concave lens.

[0055]FIG. 15 is a schematic cross sectional view of still anotherembodiment of plasma treatment apparatus also obtained by modifying theembodiments of FIGS. 1 and 9 and suitably adapted to surface treatmentof a convexo-concave lens.

[0056]FIG. 16 is a schematic cross sectional view of another embodimentof plasma treatment apparatus according to the invention.

[0057]FIG. 17 is a schematic perspective view of a radial line slotantenna having a spherical profile.

[0058]FIGS. 18A, 18B and 18C are schematic side views of differentconductor antennas having a spherical profile.

[0059]FIG. 19 is a schematic cross sectional view of still anotherembodiment of plasma treatment apparatus according to the invention.

[0060]FIG. 20 is a schematic plan view of the microwave supply means ofthe embodiment of FIG. 19.

[0061]FIG. 21 is a schematic cross sectional view of one of themicrowave emitting members of FIG. 20 taken along line 21-21.

[0062]FIG. 22 is a schematic plan view of one of the conductor flatplate antennas of the embodiment of FIG. 19.

[0063]FIG. 23 is a schematic cross sectional view of still anotherembodiment of plasma treatment apparatus according to the invention.

[0064]FIG. 24 is a schematic cross sectional view of a known plasmatreatment apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0065]FIG. 1 is a schematic cross sectional view of an embodiment ofplasma treatment apparatus according to the invention.

[0066] Referring to FIG. 1, 101 denotes a pressure reducible container,the internal pressure of which can be reduced to a level between about1.33×10⁻⁶ Pa and about 133 Pa by means of an evacuation means (notshown) connected to the exhaust port 102 of the container 101.

[0067] The container 101 is provided with a number of gas supply ports103, through which gas can be fed into the container and turned intoplasma by means of high frequency energy in the frequency band of UHF,SHF or EHF such as that of a microwave.

[0068] The container 101 contains therein a holder 104 for carrying andholding an object of treatment W. The holder 104 is vertically movableand revolvable so that it may take a selected height. A bias potentialmay be applied to the holder 104. A holder drive mechanism 105 isarranged-to drive the holder to move vertically and/or revolve.

[0069] In FIG. 1, 106 denotes a non-planar dielectric plate providedwith a number of gas supply ports 108 and made of a dielectricsubstance. It operates as a shower head for supplying gas.

[0070] The dielectric plate is made of a dielectric substance that cantransmit microwaves. Materials that can be used for the dielectric plateinclude aluminum oxide (Al₂O₃), silicon oxide (SiO₂), aluminum nitride(AlN), calcium fluoride (CaF₂) and magnesium fluoride (MgF) that may ormay not show a stoichiometric ratio.

[0071] The gas fed into the container 101 from a gas supply system (notshown) by way of the gas supply ports 103 is directed into plasmaprocessing space A by way of gas supply paths 108 arranged in thedielectric plate 106.

[0072] The dielectric plate 106 has a concave and spherical lowersurface because it is adapted to treat the surface of a convex lenshaving a spherical profile. The object W is made of silicon oxide orcalcium fluoride.

[0073] In FIG. 1, 115 denotes an O-ring for securing a vacuum conditioninside the treatment space.

[0074]FIG. 2 is a schematic perspective view of the non-planardielectric plate 106 of the embodiment of FIG. 1. Note that the lowersurface located vis-a-vis the object of treatment in FIG. 1 is made toface upward in FIG. 2. Also note that gap separating the gas supplypaths 108 of the dielectric plate 106 and the object of treatment Wshows a constant value for all the paths, which is found within apermissible range.

[0075] A microwave is introduced in a manner as described below.

[0076] The microwave supply means comprises a coaxial tube 110, aconductor flat plate antenna 111 having a number of slots, a dielectricmember 113 operating as microwave supply window and a dielectric plate106. The inner conductor 110 a of the coaxial tube 110 is connected tothe center of the conductor flat plate antenna 111. Reference numeral114 in FIG. 1 denotes an antenna adapter.

[0077] The microwave generated by a microwave oscillator (not shown) istransmitted or propagated to the conductor flat plate antenna 111 thatoperates as microwave supply plane by way of the coaxial tube 110. Themicrowave that has been transmitted is then emitted through the slotsarranged in the antenna 111.

[0078]FIG. 3 is a schematic plan view of the conductor flat plateantenna 111 of the embodiment of FIG. 1.

[0079] A number of slots 111S are arranged coaxially or helically orvertically in the conductor flat plate antenna as shown in FIG. 3. Eachof the slots comprises a pair of notches directed to intersect eachother, the lengths and the intervals of the notches being appropriatelyselected as a function of wavelength of the microwave and the plasmaintensity required for the surface treatment.

[0080] Such an antenna is referred to as radial line slot antenna anddescribed in detail in Japanese Patent Application Laid-Open No.1-184923 and U.S. Pat. No. 5,034,086 as well as in Japanese PatentApplications Laid-Open Nos. 8-111297 and 4-48805.

[0081] Now, an operation of forming a thin film on a lens having aspherical surface by means of the above embodiment of plasma treatmentapparatus according to the invention will be described below.

[0082] Firstly, a convex lens is placed on the holder 104 in theapparatus and securely held in position with the surface to be treatedof the lens facing upward.

[0083] Then, the holder 104 is raised by means of the drive mechanism105 until the surface 106 a of the microwave supply means facing theobject of treatment and the opposite surface Wa to be treated of theobject is found between 10 mm and 50 mm.

[0084] Then, after reducing the internal pressure of the container 101to about 1.3×10⁻⁵ Pa by means of the evacuation pump connected to theexhaust port 102, processing gas is fed into the plasma processing spaceA by way of the gas supply paths 108 as gas is supplied from the supplysystem connected to the gas supply port 103. The internal pressure ofthe container is held to an appropriately selected level between 13.3 Paand 1.33×10³ Pa by controlling both the gas supply rate and the gasexhaust rate. Then, a microwave is supplied to the conductor flat plateantenna 111 by way of the coaxial tube 110 as the microwave is suppliedfrom the microwave oscillator connected to the coaxial tube 110. Themicrowave emitted from the conductor flat plate antenna 111 is led intothe plasma processing space A through the dielectric member 113 and thedielectric plate 106.

[0085] Thus, a glow discharge occurs to produce gas plasma in the plasmaprocessing space A. The produced plasma will show a high density ofbetween 10¹¹ and 10¹³ cm⁻³ so that a dense and high quality film will beformed on the lens.

[0086] With this embodiment, since the width, or the gap Tg, of theplasma processing space is less than 10 mm (more specifically less than50 mm and much less than 10 mm), any reaction by-products produced inthe space A can be quickly removed with exhaust gas so that the formedfilm will be practically free from pin holes and hence of high quality.The fact that the gap Tg is less than 50 mm allows the use of a vacuumpump having a relatively small evacuation capacity for quickly removingthe reaction by-products.

[0087]FIG. 4 is a graph showing the relationship between the gap Tgseparating the dielectric plate and the object of treatment and theplasma density in the embodiment of FIG. 1. It will be seen that, whenTg is smaller than 10 mm, the plasma density changes significantlydepending on Tg, and when Tg exceeds 50 mm, the plasma density fallsabruptly. However, the relative density difference of the plasma isfound below 20% so that consequently a uniform film will be formed whenthe gap is found within the range of 10 mm<Tg≦50 mm sandwiched between apair of inflection points in FIG. 4.

[0088]FIG. 5 is a schematic side view of the non-planar profile of thedielectric plate 106 used in the embodiment of FIG. 1 when treating thesurface of a convex lens whose largest thickness Ts is less than 40 mm.In FIG. 5, Ts denotes the largest thickness of the convex lens to betreated and rs and ds respectively denote the radius of curvature andthe radius of aperture of the convex lens.

[0089] On the other hand, ra denotes the radius of curvature of thespherical microwave emitting surface 106 a of the dielectric plate 106and Ta and da respectively denote the shortest and longest distancesbetween the center of the convex lens and the spherical microwaveemitting surface 106 a.

[0090] With this embodiment, it is sufficient for the distance betweenthe surface Wa of the convex lens and the microwave emitting surface 106a to be found between 10 mm and 50 mm and hence the microwave emittingsurface is not necessarily required to be spherical so that it mayalternatively be flat. However, the use of a surface having a contoursimilar to that of the surface of the convex lens is selected in orderto remove gas efficiently from the gap and realize an enhanced degree ofuniformity for the surface treatment.

[0091]FIG. 6 is a schematic side view of the non-planar profile of thedielectric plate used in the embodiment of FIG. 1 when treating thesurface of a convex lens whose largest thickness is more than 40 mm.

[0092] The spherical microwave emitting surface 106 a of the dielectricplate 106 is so arranged that its radius of curvature ra is greater thanthe radius of curvature rs of the convex lens to be treated.

[0093] The holder 104 is lifted until the shortest distance Tg betweenthe top of the surface Wa of the convex lens W and the microwaveemitting surface 106 a is found between 10 mm and 50 mm. It is soarranged that the distance Tg′ between the surface of the convex lensand the microwave emitting surface along the edge of the convex lens isalso found between 10 mm and 50 mm under this condition.

[0094] The dielectric plate having such a spherical surface is designedin a manner as will be discussed in greater detail hereinafter.

[0095] The relationship between the dielectric plate 106 having aspherical surface and the object of treatment W having also a sphericalsurface will be defined as follows when controlling the distance Tgbetween the spherical surface of the dielectric plate and that of theobject of treatment to about less than 40 mm by modifying the radius ofcurvature ra and the aperture diameter da of the dielectric plate 106 asa function of the radius of curvature rs and the radius of aperture dsof the object of treatment W. Assume that the object of treatment has athickness of Ts.

[0096] 1) If Ts is not greater than 40 mm or 0<Ts≦40 mm (see FIG. 5) andthe thickness, the radius of curvature and the radius of aperture of theobject of treatment having a spherical surface are respectively Ts, rsand ds, whereas those of the dielectric plate also having a sphericalsurface are respectively Ta, ra and da, a dielectric plate whose Ta, raand da are defined by the following expressions may well be used.

0 mm≦Tg≦50 mm and 10 mm≦dg≦50 mm

[0097] or

10 mm≦ds≦{square root}{square root over (Ta(2ra−Ta))}−{squareroot}{square root over ( Ts)}(2rs−Ts)≦50 mm

[0098] 2) If Ts is greater than 40 mm or Ts>40 mm (see FIG. 6) andTa=ra=da (the dielectric plate is semispherical), provided that theheight of the object of treatment holder is hs (>0), the height hs maywell be so selected as to satisfy the following expressions,

10 mm≦Ta−(Ta+hs)≦50 mm

[0099] provided that the radial relationship between the object oftreatment and the dielectric plate is Wa-s.

10 mm≦Wa−s≦50 mm

[0100] therefore

10 mm≦{square root}{square root over ((ra ² −hs ²)−ds)}≦50 mm.

[0101] 3) As for an object of treatment having a spherical surface and aparticular profile, Ta, ra and da of the dielectric plate having aspherical surface may well be so selected as to make the distance Tgbetween the dielectric plate and the object of treatment also having aspherical surface satisfy the relationship of 10≦Tg≦50 regardless of theabove requirements.

[0102] The above method of designing the dielectric plate having aspherical surface corresponding to the contour of the spherical surfaceof the object of treatment is described only as an example and it may beneedless to say that the dielectric plate can be designed in variousdifferent ways.

[0103]FIGS. 7, 8A and 8B are schematic views of an embodiment obtainedby modifying the embodiment of FIG. 1 so as to make the microwaveemitting surface of the dielectric plate 106 show a stepped profile.Note, however, that the stepped microwave emitting surface shows acontour approximated to that of the spherical surface of the dielectricplate. FIG. 7 is a cross sectional view of the embodiment and FIGS. 8Aand 8B are respectively a schematic cross sectional view and a schematicplan view of the dielectric plate shown in FIG. 7.

[0104]FIG. 9 is a schematic cross sectional view of another embodimentof plasma treatment apparatus obtained by modifying the embodiment ofFIG. 1 and suitably adapted to surface treatment of an object oftreatment W, which is a concave lens. As shown, the dielectric plate 106shows a contour similar to that of a concave lens and has a convex lowersurface. The dielectric plate having such a convex microwave emittingsurface may also be designed in a manner as described above by referringto a dielectric plate having a concave microwave emitting surfaceadapted to a convex lens. The lens is also arranged at a position thatsatisfies the relationship of 10≦Tg≦50.

[0105]FIG. 10 is a graph showing the relationship between the radialdistance of the conductor flat plate antenna and the plasma density inembodiments having respective dielectric plates 106 with a convexcontour, a concave contour and a flat contour respectively for emittinga microwave, when a radial line slot antenna having the slots arrangedradially substantially uniformly and coaxially on the circular conductorflat plate 111 of the antenna is used. It will be seen that the plasmadensity changes as a function of the distance from the radial center ofthe microwave antenna showing a suitable slot distribution pattern.

[0106] Since the absolute value of the horizontal axis depends on thelocation of the probe, FIG. 10 should be used to see the relativechanges in the plasma density.

[0107] It will be seen that a conductor flat plate antenna having slotsand showing a distribution pattern as indicated by white squares in FIG.10 should be used because the plasma density produced by such an antennafor a microwave is radially substantially constant when the microwave isemitted from the antenna only by way of a flat dielectric member such asa dielectric thin plate member 113.

[0108] However, when the object of treatment shows a convex surface andhence the dielectric plate 106 shows a concave surface, the conductorflat plate antenna preferably shows a slot distribution pattern thatproduces a biased emission density of microwave that is low at thecenter and high along the outer periphery as indicated by black squaresin FIG. 10. Conversely, when the dielectric plate 106 shows a convexsurface, the conductor flat plate antenna preferably shows a slotdistribution pattern that produces a biased emission density ofmicrowave that is high at the center and low along the outer peripheryas indicated by black circles in FIG. 10.

[0109]FIG. 11 is a schematic cross sectional view of still anotherembodiment of plasma treatment apparatus using a non-planar dielectricplate 106 with a microwave emitting surface having a stepped andsubstantially convex profile.

[0110]FIGS. 12A and 12B are a schematic cross sectional view and aschematic plan view of the dielectric plate 106 of the apparatus of FIG.11. FIG. 12A is a schematic cross sectional view and FIG. 12B is aschematic plan view of the dielectric plate 106. Again the microwaveemitting surface of the dielectric plate is macroscopically non-planar.

[0111]FIG. 13 is a schematic cross sectional view of still anotherembodiment of plasma treatment apparatus obtained by modifying theembodiment of FIG. 1 and suitably adapted to surface treatment of aconvexo-convex lens, as the dielectric plate 106 has microwave emittingsurfaces that are vertically symmetric.

[0112] In FIG. 13, the components that are arranged verticallysymmetrically are denoted by respective reference numerals that areaffixed by A or B. Thus, there are shown non-planar dielectric plates106A, 106B provided with respective gas supply paths 108A, 108B, coaxialtubes 110A, 110B, conductor flat plate antennas 111A, 111B and so on.

[0113] In this embodiment, the holder 104 is secured to the center ofthe apparatus, which is also the center of vertical symmetry to hold theobject of treatment W along the periphery thereof. A bias potential canbe applied to the holder 104. As in the case of the embodiment describedabove and adapted to surface treatment of a convex lens, a dense andfine film can be formed simultaneously on the opposite sides of the lensby means of this embodiment. Such a film shows an excellentintra-surface uniformity and is substantially free from defects. Thedesign procedure of this embodiment is same as the one described aboveby referring to the surface treatment of a convex lens.

[0114] A pair of exhaust ports 102 are arranged laterally andsymmetrically at the middle of the height of the apparatus. Otherwise,the embodiment has a configuration same as that of the precedingembodiments.

[0115]FIG. 14 is a schematic cross sectional view of still anotherembodiment of plasma treatment apparatus obtained by modifying theembodiment of FIG. 9 and suitably adapted to surface treatment of aconcavo-concave lens, as it has microwave emitting surfaces that arevertically symmetric.

[0116]FIG. 15 is a schematic cross sectional view of still anotherembodiment of plasma treatment apparatus obtained by modifying theembodiments of FIGS. 1 and 9 and suitably adapted to surface treatmentof a convexo-concave lens. In FIGS. 14 and 15, the components same asthose of FIG. 13 are denoted respectively by the same reference symbols.The effect of each of these embodiments is identical with that of theembodiment of FIG. 13 and they may be designed by following the abovedescribed design procedure.

[0117] Thus, as will be clear from the above description, the aboveembodiments of plasma treatment apparatus according to the invention cantreat not only the surface of a spherical convex lens but also that of aspherical concave lens only by replacing the microwave supply meanshaving an antenna with a concave profile with a microwave supply meanshaving an antenna with a convex profile.

[0118]FIG. 16 is a schematic cross sectional view of another embodimentof plasma treatment apparatus according to the invention.

[0119] Referring to FIG. 16, 101 denotes a pressure reducible container,the internal pressure of which can be reduced to a level between about1.33×10⁻⁶ Pa and about 133 Pa by means of an evacuation means (notshown) connected to the exhaust port 102 of the container 101.

[0120] The container 101 is provided with a number of gas supply ports103, through which gas can be fed into the container and turned intoplasma by means of high frequency energy in the frequency band of UHF,SHF or EHF such as that of a microwave.

[0121] The container 101 contains therein a holder 104 for carrying andholding an object of treatment W. The holder 104 is vertically movableand revolvable so that it may take a selected height. A bias potentialmay be applied to the holder 104. A holder drive mechanism 105 isarranged to drive the holder to move vertically and/or revolve.

[0122] In FIG. 16, 106 denotes a non-planar dielectric plate providedwith a number of gas supply ports 108 and made of a dielectricsubstance.

[0123] The dielectric plate 106 is made of a dielectric substance thatcan transmit microwaves. Materials that can be used for the dielectricplate include aluminum oxide, silicon oxide, aluminum nitride, calciumfluoride and magnesium fluoride.

[0124] The gas fed into the container 101 from a gas inlet port 107connected to a gas supply system (not shown) is directed into plasmaprocessing space A by way of gas supply port 103 arranged in thedielectric plate 106.

[0125] The dielectric plate 106 has a concave and spherical lowersurface because it is adapted to treat the surface of a convex lenshaving a spherical profile.

[0126] In FIG. 16, 115 denotes an O-ring for securing a vacuum conditioninside the treatment space.

[0127] A microwave is introduced in a manner as described below.

[0128] The microwave supply means comprises a coaxial tube 110, aconductor antenna 111 having a spherical surface and a number of slotsand a dielectric thin film 113 operating as microwave supply window. Theinner conductor 110 a of the coaxial tube 110 is connected to the centerof the conductor antenna 111. Reference numeral 114 in FIG. 16 denotesan antenna adapter.

[0129] The microwave generated by a microwave oscillator (not shown) istransmitted to the conductor antenna 111 by way of the coaxial tube 110.The microwave that has been transmitted is then emitted through theslots arranged in the antenna 111.

[0130] A microwave supply means as used for this embodiment is obtainedby bending a radial line slot antenna (RLSA) and described in detail inJapanese Patent Application Laid-Open No. 1-184923 and U.S. Pat. No.5,034,086 as well as in Japanese Patent Applications Laid-Open Nos.8-111297 and 4-48805 to show a spherical surface.

[0131]FIG. 17 is a schematic perspective view of an RLSA having aspherical surface and realized by coaxially or helically arranging anumber of slots 111S in a spherical (semispherical to be more accurate)conductor 111. The inner conductor 110 a of the coaxial tube 110 isconnected to the center of the conductor antenna 111.

[0132] Each of the slots 111S comprises a pair of notches directed tointersect each other, the lengths and the intervals of the notches beingappropriately selected as a function of wavelength of the microwave andthe plasma intensity required for the surface treatment.

[0133]FIGS. 18A through 18C are schematic side views of differentconductor antennas having a spherical profile that can be used for thepurpose of the invention.

[0134]FIG. 18A shows an antenna showing a proper semispherical profileobtained by dividing a ball into two equal halves.

[0135]FIG. 18B shows an antenna showing a spherical profile that is partof a ball.

[0136]FIG. 18C shows an antenna having a spherical and convex profileand adapted to cover a concave lens.

[0137] While the profile of each of the slots is not shown in theantennas of FIGS. 18A through 18C, slots as shown in FIG. 17 maypreferably be used for them.

[0138] Now, an operation of forming a thin film on a lens having aspherical surface by means of the above embodiment of plasma treatmentapparatus according to the invention will be described below.

[0139] Firstly, a convex lens is placed on the holder 104 in theapparatus and securely held in position with the surface to be treatedof the lens facing upward.

[0140] Then, the holder 104 is raised by means of the drive mechanism105 until the surface 106 a of the microwave supply means facing theobject of treatment and the opposite surface Wa to be treated of theobject is found between 10 mm and 50 mm.

[0141] Then, after reducing the internal pressure of the container 101to about 1.3×10⁻⁵ Pa by means of the evacuation pump connected to theexhaust port 102, processing gas is fed into the plasma processing spaceA by way of the gas blow-in ports 103 as gas is supplied from the supplysystem connected to the gas supply ports 107. The internal pressure ofthe container is held to an appropriately selected level between 13.3 Paand 1.33×10³ Pa by controlling both the gas supply rate and the gasexhaust rate. Then, a microwave is supplied to the conductor antenna 111having a spherical surface by way of the coaxial tube 110 as themicrowave is supplied from the microwave oscillator connected to thecoaxial tube 110.

[0142] Thus, a glow discharge occurs to produce gas plasma in the plasmaprocessing space A. The produced plasma will show a high density ofbetween 10¹¹ and 10¹³ cm⁻³ so that a dense and high quality film will beformed on the lens.

[0143] With this embodiment, since the width, or the gap Tg, of theplasma processing space is less than 10 mm (more specifically less than50 mm and much less than 10 mm), any reaction by-products produced inthe space A can be quickly removed with exhaust gas so that the formedfilm will be practically free from pin holes and hence of high quality.

[0144] The relationship between the gap Tg separating the dielectricplate 106 and the object of treatment W and the plasma density in theembodiment of FIG. 16 also conforms to the graph of FIG. 4. It will beseen that, when Tg is smaller than 10 mm, the plasma density changessignificantly depending on Tg, and when Tg exceeds 50 mm, the plasmadensity falls abruptly. However, the relative density difference of theplasma is found below 20% so that consequently a uniform film will beformed when the gap is found within the range of 10 mm<Tg≦50 mmsandwiched between a pair of inflection points in FIG. 4.

[0145] Thus, the above embodiment of plasma treatment apparatusaccording to the invention can treat not only the surface of a sphericalconvex lens but also that of a spherical concave lens only by replacingthe microwave supply means having an antenna with a concave profile witha microwave supply means having an antenna with a convex profile.

[0146]FIG. 19 is a schematic cross sectional view of still anotherembodiment of plasma treatment apparatus according to the invention.

[0147] Referring to FIG. 19, 101 denotes a pressure reducible container,the internal pressure of which can be reduced to a level between about1.33×10⁻⁶ Pa and about 133 Pa by means of an evacuation means (notshown) connected to the exhaust port 102 of the container 101.

[0148] The container 101 is provided with a number of gas blow-in ports103, through which gas can be fed into the container and turned intoplasma by means of high frequency energy in the frequency band of UHF,SHF or EHF such as that of a microwave.

[0149] The container 101 contains therein a holder 104 for carrying andholding an object of treatment W. The holder 104 is vertically movableand revolvable so that it may take a selected height. A bias potentialmay be applied to the holder 104. A holder drive mechanism 105 isarranged to drive the holder to move vertically and/or revolve.

[0150] In FIG. 19, 200 denote microwave emitting members and 201 denotesealing members made of ceramic for sealing the gaps separating themicrowave emitting members of the embodiment. Reference numeral 115denotes an O-ring.

[0151] The gas fed into the container 101 through a gas supply ports 107connected to a gas supply system (not shown) is directed into plasmaprocessing space A by way of gas blow-in ports 103 after passing throughthe gas supply paths 108 arranged in a dielectric member 202.

[0152] This embodiment is adapted to treat the surface of a convex lenshaving a spherical profile.

[0153]FIG. 20 is a schematic plan view of the microwave supply means ofthe embodiment of FIG. 19.

[0154] The microwave supply means of this embodiment is an integratedentity of five rectangular microwave emitting members 200 arranged in amanner as shown in FIG. 20.

[0155]FIG. 21 is a schematic cross sectional view of the microwavesupply means of FIG. 20 taken along line 21-21, showing only the centralmicrowave emitting member 200 in cross section. All the remainingmicrowave emitting members 200, though having a different profile, havea structure same as that of the member of FIG. 21.

[0156] Referring to FIG. 21, 211 denotes a conductor flat plate antennahaving a number of slots. The inner conductor 110 a of a coaxialwaveguide 110 is connected to the conductor flat plate antenna 211 at apoint near the center of the latter, while the conductor flat plateantenna 211 is covered at an outer peripheral end thereof by a conductorcover 215 connected to the outer conductor 110 b of the coaxialwaveguide 110.

[0157] A dielectric plate 210 that transmits microwaves is arranged onthe microwave emitting surface of the conductor flat plate antenna 211.If necessary, another dielectric member 212 may be arranged on theopposite surface of the conductor flat plate antenna 211. The dielectricmember 212 may be held in contact with the antenna 211 or separated fromthe latter by a space. The dielectric plate 210 is typically made of amaterial selected from alumina, quartz, aluminum nitride, calciumfluoride and magnesium fluoride.

[0158]FIG. 22 is a schematic plan view of the conductor flat plateantenna 211 having a number of coaxially or vertically arranged slots211S.

[0159] Such an antenna is referred to as radial line slot antenna anddescribed in detail in Japanese Patent Application Laid-Open No.1-184923 and U.S. Pat. No. 5,034,086 as well as in Japanese PatentApplications Laid-Open Nos. 8-111297, 4-48805 and 5-22025.

[0160] All the distances Tg between the microwave emitting surfaces ofthe microwave emitting members 200 and the object of treatment W aremade to show a substantially constant value, which is found within apermissible range, e.g., between 10 mm and 50 mm.

[0161] A microwave is introduced in a manner as described below.

[0162] The microwave generated by a single microwave generator (notshown) is divided into five, which are then transmitted to therespective conductor flat plate antennas 211 by way of the respectivecoaxial tubes 110.

[0163] The microwave transmitted to each of the antenna 211 by way ofthe slots of the antenna will then emitted.

[0164] Now, an operation of forming a thin film on a lens having aspherical surface by means of the above embodiment of plasma treatmentapparatus according to the invention will be described below.

[0165] Firstly, a convex lens is placed on the holder 104 in theapparatus and securely held in position with the surface to be treatedof the lens facing upward.

[0166] Then, the holder 104 is raised by means of the drive mechanismuntil the gap Tg separating the surface of the microwave supply meansfacing the object of treatment and the opposite surface to be treated ofthe object is found between 10 mm and 50 mm.

[0167] Then, after reducing the internal pressure of the container 101to about 1.3×10⁻⁵ Pa by means of the evacuation pump connected to theexhaust port 102, processing gas is fed into the plasma processing spaceA by way of the gas supply paths 108 and the gas blow-in ports 103 asgas is supplied from the supply system connected to the gas supply ports107. The internal pressure of the container is held to an appropriatelyselected level between 13.3 Pa and 1.33×10³ Pa by controlling both thegas supply rate and the gas exhaust rate. Then, a microwave is suppliedto the conductor flat plate antennas 211 by way of the coaxial tube 110as the microwave is supplied from the microwave oscillator connected tothe coaxial tube 110.

[0168] Thus, a glow discharge occurs to produce gas plasma in the plasmaprocessing space A. The produced plasma will show a high density ofbetween 10¹¹ and 10¹³ cm⁻³ so that a dense and high quality film will beformed on the lens.

[0169] With this embodiment, since the width, or the gap Tg, of theplasma processing space is less than 10 mm (more specifically less than50 mm and much less than 10 mm), any reaction by-products produced inthe space A can be quickly removed with exhaust gas so that the formedfilm will be practically free from pin holes and hence of high quality.

[0170] The relationship between the gap Tg separating the dielectricplate 106 and the object of treatment W and the plasma density in theembodiment of FIG. 16 also conforms to the graph of FIG. 4. It will beseen that, when Tg is smaller than 10 mm, the plasma density changessignificantly depending on Tg, and when Tg exceeds 50 mm, the plasmadensity falls abruptly. However, the relative density difference of theplasma is found below 20% so that consequently a uniform film will beformed when the gap is found within the range of 10 mm<Tg≦50 mmsandwiched between a pair of inflection points in FIG. 4.

[0171]FIG. 23 is a schematic cross sectional view of still anotherembodiment of plasma treatment apparatus according to the invention,showing the positional relationship between the microwave emittingmembers 200 and the object of treatment W.

[0172] Referring to FIG. 23, a regulator means 201 a is arranged betweenany two adjacently located microwave emitting members 200 to regulatethe angle a between the microwave emitting members 200. The regulatormeans 201 a has an expandable bellows or diaphragm and an O-ring isarranged along the boundary of each of the emitting members 200 toproduce an airtight sealing effect. An antenna cooling space 214 isformed between the conductor flat plate antenna 211 and thecorresponding dielectric member 210 of each of the microwave emittingmembers 200. Reference numerals 216 and 217 denote members made of adielectric substance and adapted to rigidly hold the dielectric members210.

[0173] The gap Tg is made to be found within a range between 10 mm and50 mm by regulating the angle α and vertically moving the holder 104.

[0174] Thus, convex lenses having different radii of curvature can beprocessed for surface treatment by means of the above describedembodiment.

[0175] Additionally, the above described embodiment of plasma treatmentapparatus according to the invention can treat not only the surface of aspherical convex lens but also that of a spherical concave lens only byreplacing the microwave supply means having an antenna with a concaveprofile with a microwave supply means having an antenna with a convexprofile as shown in FIGS. 9 through 12A and 12B.

[0176] While the upper surface of the dielectric plate 106 is planar andthe lower surface is curved in the embodiment of FIG. 1, the uppersurface of the dielectric plate 106 may be curved to make the dielectricplate 106 show a uniform thickness between the upper and lower surfaces.

[0177] Similarly, the upper surface of the dielectric plate 106 in FIG.7 may have a stepped profile.

[0178] Likewise, the upper surface of the dielectric plate 106 in FIG. 9may be made to show a concave profile.

[0179] In short, the profile of the dielectric plate is not limited tothose illustrated in the drawings, which merely exemplify preferredembodiments.

[0180] Objects of treatment W that can be treated by means of anapparatus according to the invention include those that are made of amaterial selected from insulating and transparent materials such assynthetic fused silica (SiO₂) and fluorite (CaF₂) and those made of amaterial selected from electrically conductive andnon-light-transmitting materials such as aluminum. The former materialsare typically used for convex lenses, concave lenses, reflectors andwindow members, whereas the latter materials are typically used forreflectors.

[0181] Rays of light that can be converged, transmitted and/or reflectedby an optical part according to the invention include ultraviolet rayssuch as ArF excimer laser, KrF excimer laser or i-rays, rays of visiblelight and infrared rays.

[0182] Surface treatment operations that can be conducted by means of anapparatus according to the invention include thin film formation, plasmacleaning and plasma etching. An apparatus according to the invention isadvantageously adapted to form thin film of a material such as aluminumoxide, silicon oxide, tantalum oxide, magnesium oxide, aluminum fluorideand magnesium fluoride.

[0183] Since thin film is formed by plasma CVD, source gases that can beused for the purpose of the invention include organic aluminum compoundssuch as trimethylaluminum (TMA), triisobutylaluminum (TiBA) anddimethylaluminumhalide (DMAH), silicon compounds such as SiH₄, Si₂H₆,SiF₄ and tetraethylorthosilicate (TEOS), organic magnesium compoundssuch as bisethylcyclopentadienylmagnesium and tantalum compounds.Preferably, an oxidizing gas such as oxygen, nitrogen oxide, fluorineand NF₃ is added to the source gas. If necessary, hydrogen, helium,neon, argon, xenon or krypton gas may also be added to the source gas.

[0184] For the purpose of the invention, the microwave generator may bean ordinary microwave generator adapted to generate a microwave with afrequency of 2.45 GHz, 5,0 GHz or 8.3 GHz.

EXAMPLE 1

[0185] A convex lens of synthetic fused silica having a polishedspherical surface was placed on and rigidly secured to the holder 104 ofthe apparatus of FIG. 1.

[0186] Then, the holder 104 was lifted by operating the drive mechanism105 and then rigidly held to a position where the gap Tg was found to bebetween 20 and 30 mm. After reducing the internal pressure of thealuminum container 1 to 1.3×10⁴ Pa, the holder 104 was made to revolve.Gasified TMA and O₂ were then introduced into the container, when theinternal pressure was reduced further to 13.3 Pa and a microwave wassupplied to generate plasma. As a result, an aluminum oxide film wasformed on the spherical convex surface of the quartz.

EXAMPLE 2

[0187] A convex of synthetic fused silica lens having a polishedspherical surface was placed on and rigidly secured to the holder 104 ofthe apparatus of FIG. 16.

[0188] Then, the holder 104 was lifted by operating the drive mechanism105 and then rigidly held to a position where the gap Tg was found to bebetween 20 and 30 mm. After reducing the internal pressure of thealuminum container 1 to 1.3×10⁴ Pa, the holder 104 was made to revolve.Gasified TMA and O₂ were then introduced into the container, when theinternal pressure was reduced further to 13.3 Pa and a microwave wassupplied to generate plasma. As a result, an aluminum oxide film wasformed on the spherical convex surface of the quartz.

EXAMPLE 3

[0189] A convex lens of synthetic fused silica having a polishedspherical surface was placed on and rigidly secured to the holder 104 ofthe apparatus of FIG. 19.

[0190] Then, the holder 104 was lifted by operating the drive mechanism105 and then rigidly held to a position where the gap Tg was found to bebetween 20 and 30 mm. After reducing the internal pressure of thealuminum container 1 to 1.3×10⁴ Pa, the holder 104 was made to revolve.Gasified TMA and O₂ were then introduced into the container, when theinternal pressure was reduced further to 13.3 Pa and a microwave wassupplied to generate plasma. As a result, an aluminum oxide film wasformed on the spherical convex surface of the quartz.

[0191] When F₂ gas was used in place of O₂ gas, a high quality aluminumfluoride film was formed on the surface of the quartz lens.

[0192] As described above in detail, according to the invention, thesurface of an optical part having a concave or convex surface to betreated can be treated uniformly by means of high density microwaveplasma.

What is claimed is:
 1. A plasma treatment apparatus for treating asurface of an object of treatment, comprising a container, a gas supplymeans for supplying gas into the container for plasma excitation, anevacuation means for evacuating the inside of said container, and amicrowave supply means for supplying a microwave into said container,the surface of said microwave supply means located opposite to saidobject of treatment being a non-planar surface having a contourcorresponding to that of the surface to be treated of said object oftreatment and said non-planar surface being formed of amicrowave-transmitting dielectric.
 2. A plasma treatment apparatusaccording to claim 1, wherein gas is supplied through a plurality ofopenings arranged on said non-planar surface.
 3. A plasma treatmentapparatus according to claim 1, wherein said microwave supply means hasan antenna made of a flat plate of a conductor and having a number ofslots.
 4. A plasma treatment apparatus according to claim 1, whereinsaid non-planar surface is a convex or concave spherical surface formedon the microwave-transmitting dielectric.
 5. A method of manufacturingan optical part comprising a step of treating a concave or convexsurface of the optical part by means of a plasma treatment apparatusaccording to claim
 1. 6. A plasma treatment apparatus for treating asurface of an object of treatment, comprising: a container; a gas supplymeans for supplying gas into the container for plasma excitation; and anevacuation means for evacuating the inside of said container, a part ofthe walls of said container being made of a dielectric plate of amaterial adapted to transmit microwaves, said dielectric plate having aconvex or concave spherical surface with a predetermined radius ofcurvature, an antenna for emitting a microwave and an electrode adaptedto hold the object of treatment being arranged respectively at theoutside and at the inside of said container to sandwich the dielectricplate.
 7. A plasma treatment apparatus according to claim 1 or 6,wherein the dielectric plate has a shower-head-like profile providedwith a plurality of gas supply holes for evenly supplying gas to thesurface of said object of treatment.
 8. A plasma treatment apparatusaccording to claim 6, wherein the radius of curvature and the radius ofaperture of said dielectric plate are variable.
 9. A plasma treatmentapparatus according to claim 1 or 6, wherein the distance between theinner surface of said dielectric plate and the surface to be treated ofsaid object of treatment is between 10 mm and 50 mm.
 10. A plasmatreatment apparatus according to claim 1 or 6, wherein the relativedensity difference of the plasma in said surface to be treated issuppressed to less than about 20%.
 11. A plasma treatment apparatusaccording to claim 6, wherein the variations in the plasma density dueto the variations in the thickness of said dielectric plate can becorrected by making at least the size, the profile or the number of theslots formed in said antenna to show a distribution pattern.
 12. Aplasma treatment apparatus according to claim 6, wherein said object oftreatment held by a support member is provided with a rotary mechanism.13. A plasma treatment apparatus according to claim 6, wherein saidnon-planar surface is a stepped surface obtained by forming coaxialsteps.
 14. A plasma treatment apparatus according to claim 6, whereinsaid gas supply means has a stepped shower-head-like profile.
 15. Aplasma treatment apparatus according to claim 6, wherein the main bodyof said antenna has a spherical or stepped profile.
 16. A plasmatreatment apparatus according to claim 6, wherein said antenna having aspherical or stepped profile is arranged within said container.
 17. Aplasma treatment apparatus according to claim 6, wherein a non-planarsurface is formed by using a plurality of such antennas.
 18. A surfacetreatment method for treating the surface of an object of treatment bymeans of an apparatus according to claim
 1. 19. A surface treatmentmethod according to claim 18, wherein said surface treatment consists informing a thin film.
 20. A method of manufacturing an optical part byusing a surface treatment method according to claim 18 and forming ananti-reflection or reflection-boosting thin film on an object oftreatment made of silicon oxide or calcium fluoride.
 21. A plasmatreatment apparatus for treating a surface of an object of treatment,comprising a container, a gas supply means for supplying gas into thecontainer for plasma excitation, an evacuation means for evacuating theinside of said container, and a microwave supply means for supplying amicrowave into said container, said microwave supply means having aplurality of microwave emitting members and its surface located oppositeto the object of treatment being directed in a predetermined directionrelative to the surface to be treated of said object of treatment.
 22. Aplasma treatment apparatus according to claim 21, wherein each of saidmicrowave emitting members include a conductor flat plate antenna havinga number of slots.
 23. A method of manufacturing an optical partcomprising a step of forming a film coat on an optical part by using anapparatus according to claim
 21. 24. A plasma treatment apparatus fortreating a surface of an object of treatment, comprising a container, agas supply means for supplying gas into the container for plasmaexcitation, an evacuation means for evacuating the inside of saidcontainer, and a microwave supply means for supplying a microwave intosaid container, the surface of said microwave supply means locatedopposite to said object of treatment being a non-planar surface having acontour corresponding to that of the surface to be treated of saidobject of treatment.
 25. A plasma treatment apparatus according to claim24, wherein said gas supply means includes an antenna of a conductormember having a spherical surface and slots.
 26. A plasma treatmentapparatus according to claim 25, wherein the gas blow-in port of saidgas supply means is arranged at an end of the antenna made of aconductor member having slots.
 27. A plasma treatment apparatusaccording to claim 24, wherein the distance between the inner surface ofsaid microwave supply means and the surface to be treated of said objectof treatment is between 10 mm and 50 mm.
 28. A method of manufacturingan optical part comprising a step of forming a film coat on an opticalpart by using an apparatus according to claim 24.